Ongoing important Science news thread

[Hack&Lube]

Originally Posted by octothorp

Or maybe we can purchase neurons that have been pre-populated... with, for example, memories of vacationing on mars!

As was the market for VHS and DVD, it's porn that will drive everything.

[Hemi-Cuda]

Originally Posted by Hack&Lube

Japanese going to build Space Elevator by 2050? It will probably be the Chinese by then.

http://news.discovery.com/tech/space...l#mkcpgn=otbn1

top speed of 124 mph? you'd think by the time the technology is invented to build a space elevator, they could figure out a way to not make it take a week to reach orbit

[T@T]

Originally Posted by Hemi-Cuda

top speed of 124 mph? you'd think by the time the technology is invented to build a space elevator, they could figure out a way to not make it take a week to reach orbit

The speed doesn't bother me as much as why the need to build it 22.000 miles long into space, they could go 70 miles and have the same effect of weightlessness or a couple of hundred miles and get a nice view of the earth.

[photon]

Originally Posted by T@T

The speed doesn't bother me as much as why the need to build it 22.000 miles long into space, they could go 70 miles and have the same effect of weightlessness or a couple of hundred miles and get a nice view of the earth.

Because 70 miles up the orbit isn't geosynchronous, so the station portion of the tether would orbit away minutes after you place it and break the tether.

Geostationary orbit is 22,236 miles up, if you put the station there it'll (mostly) stay where you put it in relation to a point on the earth's surface, minimizing the tension on the cable due to the station.

[Hemi-Cuda]

Originally Posted by photon

Because 70 miles up the orbit isn't geosynchronous, so the station portion of the tether would orbit away minutes after you place it and break the tether.

Geostationary orbit is 22,236 miles up, if you put the station there it'll (mostly) stay where you put it in relation to a point on the earth's surface, minimizing the tension on the cable due to the station.

with a large enough counterweight, couldn't you place the station a lot closer to the Earth?

[Hack&Lube]

Originally Posted by Hemi-Cuda

with a large enough counterweight, couldn't you place the station a lot closer to the Earth?

Yep, right into the ground

[Hack&Lube]

Originally Posted by T@T

The speed doesn't bother me as much as why the need to build it 22.000 miles long into space, they could go 70 miles and have the same effect of weightlessness or a couple of hundred miles and get a nice view of the earth.

Like Photon said, you need to get it into geosynchronous orbit. Also, It's also not about the view or weightlessness. The point is not just to create some kind of tourist attraction but a viable way of getting things into space without the need for expensive one-off expendable launch vehicles and a fortune in fuel. A real space elevator would be paydirt because it would be a lot cheaper to send up satellites or space station components and ferry passengers into space than by conventional rockets.

[photon]

Originally Posted by Hemi-Cuda

with a large enough counterweight, couldn't you place the station a lot closer to the Earth?

I suppose you could.

The counterweight acts to add tension to the rope, and has to counteract the mass of the rope itself and the mass of anything attached to the rope (the elevator, or non-moving station attached to the rope).

The tension would probably have to be insane though for a station with any size, the nice thing about a space elevator is that the station's mass can be ignored at geosynchronous orbit; gravity and centrifugal force cancel. It's basically weightless with respect to the cable system. You can build it as big as you want.

A bunch of math that's too late to try and grok here:

http://www.zadar.net/space-elevator/

[photon]

Originally Posted by Hack&Lube

A real space elevator would be paydirt because it would be a lot cheaper to send up satellites or space station components and ferry passengers into space than by conventional rockets.

For sure, even a conservative estimate would put a space elevator at an order of magnitude cheaper per kg vs. rockets.. and two orders of magnitudes if you listen to the pie in the sky guys.

[Hack&Lube]

Originally Posted by photon

For sure, even a conservative estimate would put a space elevator at an order of magnitude cheaper per kg vs. rockets.. and two orders of magnitudes if you listen to the pie in the sky guys.

Yep. One of the biggest problems with space exploration is that the vehicle needs to carry it's fuel with it which adds to the weight and amount of fuel neccessary to propel it. The chemical propellent also needs to be safe and compact which reduces it's potential and cuts down on range.

Along with the ideas of ground-based propulsion (some kind of laser that will push a vehicle into space and beyond), the space elevator can be powered by cheap, plentiful, and powerful ground based forms of energy. Perhaps even the earth's rotation can be used to transport objects into orbit and then objects can remain in place while the earth rotates around where the objects can be dropped back down into a different location on the planet down another elevator.

[octothorp]

A new hominid discovered. What's really interesting is that it existed at the same time as Lucy in a similar region, but is distinctly different, particularly in having a grasping, tree-climbing foot rather than the distance-running foot of Lucy. It seems to neatly fit a fossil record gap (likely not as an ancestor of humans but as a cousin).

http://www.cbc.ca/news/technology/st...-ethiopia.html

[starseed]

A cousin that we killed off because they are freaks.

[Bagor]

Some of the world's most commonly used pesticides are killing bees by damaging their ability to navigate and reducing numbers of queens, research suggests. Scientific groups in the UK and France studied the effects of neonicotinoids, which are used in more than 100 nations on farm crops and in gardens.

The neonicotinoids investigated in the two Science papers are used on crops such as cereals, oilseed rape and sunflowers.
Often the chemical is applied to seeds before planting. As the plant grows, the pesticide is contained in every part of it, deterring insect pests such as aphids.
But it also enters the pollen and nectar, which is how it can affect bees.
Dave Goulson from the UK's University of Stirling and colleagues studied the impact of the neonicotinoid imidacloprid on bumblebees.
They let bees from some colonies feed on pollen and sugar water containing levels of imidacloprid typically found in the wild, while others received a natural diet.
Then they placed the colonies out in the field.
After six weeks, colonies exposed to the pesticide were lighter than the others, suggesting that workers had brought back less food to the hive.
But the most dramatic effect was on queen production. The naturally-fed hives produced around 14 queens each - those exposed to the pesticide, just two.

Could be an interesting one given that the very people that stand to lose most from a significant decline in pollinators could be the people indirectly responsible for the decline.

http://www.bbc.co.uk/news/science-environment-17535769

[Daradon]

Wouldn't a space elevator be very susceptible to (terrorist/war) attacks? Even if it didn't cause a lot of damage to the surrounding area (as I'm assuming if it broke it might actually get flung out into space from the centrifugal force?) it sure would be a waste of a lot of money if it broke for whatever reason. Wouldn't be something you'd want to rebuild.

[Bring_Back_Shantz]

Okay a few people have mentioned the centrifugal force with respect to a space elevator.
That is not at all how it works.
It's not like the earth is swinging the station around and the only thing keeping it in orbit is the teather.
To figure out why that's the case, I recommend tying something to the ground and seeing if it swings around.

[photon]

Originally Posted by Daradon

Wouldn't a space elevator be very susceptible to (terrorist/war) attacks? Even if it didn't cause a lot of damage to the surrounding area (as I'm assuming if it broke it might actually get flung out into space from the centrifugal force?) it sure would be a waste of a lot of money if it broke for whatever reason. Wouldn't be something you'd want to rebuild.

For sure, I'm pretty sure I've even read that scenario in a few different sci-fi books.

The station itself wouldn't go anywhere (since it's in geosynchronous orbit), as long as you disconnected from the counterweight soon enough.

And imagine 20,000km of cable falling to earth (if you manged to sever it with a bomb in the elevator for example), even if it's thin that's still super massive. Or taking out other satellites as it flails around in space while falling.

[photon]

Originally Posted by Bring_Back_Shantz

Okay a few people have mentioned the centrifugal force with respect to a space elevator.
That is not at all how it works.
It's not like the earth is swinging the station around and the only thing keeping it in orbit is the teather.
To figure out why that's the case, I recommend tying something to the ground and seeing if it swings around.

Well in your example, gravity has something to do with it not flying around, along with the mass of the thing you are tying and the length of your rope.

If that's not how it works, if you're just dropping a rope from a station, what's the counterweight for?

Centrifugal force is exactly how it works, at least for the common idea of space elevators:

From Wikipedia:

A space elevator for Earth would consist of a cable anchored to the Earth's equator, reaching into space. By attaching a counterweight at the end (or by further extending the cable upward for the same purpose), the center of mass is kept well above the level of geostationary orbit. Upward centrifugal force from the Earth's rotation ensures that the cable remains stretched taut, fully countering the downward gravitational pull. Once above the geostationary level, climbers would have weight in the upward direction as the centrifugal force overpowers gravity. (The diagram is to scale. The height of the counterweight varies by design and a typical, workable height is shown.)

I guess you could have the teather drop down and not be under tension, but you'd need the counterweight to offset the mass of the rope being dropped still and I don't know how that would work since the counterweight would just move away in a different orbit as you reeled it out to counter the tether dropping. Some kind of station keeping rockets, I don't know that seems a LOT harder to pull off. I haven't thought much about a space elevator that wasn't under tension.

[Dan02]

Originally Posted by photon

From Wikipedia:




I guess you could have the teather drop down and not be under tension, but you'd need the counterweight to offset the mass of the rope being dropped still and I don't know how that would work since the counterweight would just move away in a different orbit as you reeled it out to counter the tether dropping. Some kind of station keeping rockets, I don't know that seems a LOT harder to pull off. I haven't thought much about a space elevator that wasn't under tension.

Ahh makes so much more sense now. I thought initially you were putting the counterweight in geostationary orbit, which didn't make much sense as you mentioned.

Question though as I'm not well learned in this area. In the diagram they say the center of mass has to be above geostationary level. Wouldn't it have to be at geostationary level or the tether is going to wrap itself around the earth?

[photon]

Hm, I'm not sure about that one, I had to do some searching:

http://gassend.net/spaceelevator/cen...ass/index.html

Too late to figure it out though, I'll have to re-look at it later.

[Daradon]

Originally Posted by photon

For sure, I'm pretty sure I've even read that scenario in a few different sci-fi books.

The station itself wouldn't go anywhere (since it's in geosynchronous orbit), as long as you disconnected from the counterweight soon enough.

And imagine 20,000km of cable falling to earth (if you manged to sever it with a bomb in the elevator for example), even if it's thin that's still super massive. Or taking out other satellites as it flails around in space while falling.

Cool. Ok then, I would think that there would have to be some serious defense or counter measures built into the project. I would think it would be a very big target of opportunity for many groups. I mean, it would be awesome to have one of these built in our lifetime, probably the first step in really creating a serious space program/future space effort. But if it's so easy susceptible to attack, what's the point? You know someone is going to go after it. Especially if it's being used for space military or defense. (IE not it specifically, but to help programs in space that may or may not be defense in origin)